Sushibog is wrtten by researchers of Sushi University

Why do we use the counter “kan (貫)” for sushi?

When you sit at the counter and order nigiri a la carte, they will come out in pairs.* There is nothing wrong with counting these in the regular Japanese way “ikko,” “niko.”

*It is said that nigiri-sushi in the Edo period was bigger than it is today, and too big to eat in one bite. In the Meiji period, the custom emerged of splitting this one big portion into two to make more easily consumed portions, and this is why it is common to get sushi in sets of two. However, nowadays making one piece of nigiri-sushi at a time is not very efficient. We think it’s actually easier for the sushi restaurant to make them in sets of two. Of course, you can order them one by one.

But the sushi restaurant won’t count them like that. Formally, sushi is counted in this way: Ikkan (one), Nikan (two).

We have absolutely no idea where the custom of using the “kan” counter came from. It’s also not clear when use of that counter for sushi started.

Of course, there are theories. For example, there is a theory that back at a time when a single unit of money was called “kan.” The price for one piece of sushi was around 1 ‘kan’, and the counting method gained popularity. There is another theory that one sushi roll was counted with the counter for roll “巻” (also pronounced “kan”), then a different kanji was used for it later. However, these are just theories that were created after the fact and the mystery remains unsolved.

Even if you ask the owner of a sushi restaurant, they’ll probably cock their head to one side, think for a moment, and tell you that the “kan” mystery may never be solved.

Sushi rolls wrapped in seaweed rolls are counted in units of 本 (hon/bon/pon) in the wrapped state, and when cut with a knife, the units change to 切れ (kire). While these units are fairly straight-forward for Japanese language speakers and easy to understand, only the enigmatic 貫 (kan) remains a mystery.

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Revision date: April 29, 2020

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Do you know that there are rankings for Negitoro?

First, what do you imagine when you hear the word “negitoro”?

Most people probably think of “Negitoro Gunkan” or “Negitoro Roll” served at sushi restaurants.

But the real “negitoro” does not have leeks!

The original name for negitoro was negitoru. It translates to chip away in Japanese. The name eventually evolved to negitoro.

Here we come to the point.

The original negitoro is made from medium fatty tuna or nakaochi* chopped up finely with a knife and then mixed with chopped green onions on top. But the tuna may be switched out with filler, leading to a variety in quality of the negitoro available.

First of all, the lowest in the ranking are the offcuts of tuna that can’t be made into sashimi (mainly Yellowfin or Albacore tuna) and this is mixed with vegetable oil and minced. The type of onion used is normally green onions. You can pick this type out because it will be whitish in color. This version is normally served at conveyor belt sushi.

The medium quality uses the nakaochi of cheap Albacore tuna or Swordfish.

High quality negitoro uses the nakaochi of Pacific bluefin tuna or Southern bluefin tuna. Sometimes the green onion shoots are then rolled up inside. If you have a chance to try negitoro in Japan, we recommend you try the top quality options without a doubt. One piece will probably cost around $15 USD. But that’s the price for the real thing!

Finally, let me introduce some negitoro trivia. There is a lot of flesh on the middle bone (spine) and the surrounding area for tuna and the like. This is called “nakaochi*”. Scraping the meat from this area surrounding the spine is known as “negitoru”, which is where the word “negitoro” comes from. In other words, the name “negitoro” is not actually from the words onion (negi) and tuna belly (toro).

What is negitoro like at Sushi restaurants?

Originally, the meat from the middle cut or in between the bones of the tuna was used for negitoro. In order to get meat from these parts, the chef would have to purchase an entire tuna, or buy the cut that includes the mid-ribs. However, both of these purchases are difficult for a single sushi restaurant, so now the chef chops the meat from the body with a butcher knife until it forms a paste that is sticky and smooth from the fat in the tuna. This paste is used for negitoro.

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Revision date: July 30, 2022

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What is Kakushiaji?

Kakushiaji refers to a technique where a single seasoning (For example, sugar, vinegar, soy sauce, salt, etc.) is added to a dish. The Kakushiaji contrasts with the finished dish’s flavor, and is added in an amount too small to notice when served. This produces a clear improvement in flavor.

Examples include adding a little salt to heighten sweetness, or adding a little vinegar to a simmered dish. Sometimes these combination of flavors can be quite surprising, like adding a touch of chocolate to a curry.

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Revision date: November 7, 2018

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What is Umami?

Umami describes the delicious taste of savory flavor essences. For many years, people held to the belief that humans can taste only four basic flavors (sweet, sour, salty, bitter) unitil a japanese chemist named Kikunae Ikeda discovered a fifth flavor (glutamic acid) in the early 20th century.

The main umami ingredients are glutamic acid in seaweed, inosinic acid in dried bonito and meats, succinic acid in shellfish, guanylic acid in shiitake mushroom.

Many ingredients contain a wide variety of umami essences. In combination, they create a synergistic effect which produces an even more potent savory flavor.

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Revision date: October 31, 2018

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Automatic reply mails from Sushi University

The reply from the reservation system is based on the application by the guests autocratically. The original information of your reservation cannot be updated by our system. If there is a change, the new information will not be reflected in the following 4 automatic reply mails.

[Automatic reply mails from Sushi University]

1.The thank you mail to inform you the acceptance for your application

2.The mail to confirm your reservation

3.The mail to reconfirm your reservation : will be delivered the day before Sushi University

4.(only if) The mail to inform you the acceptance for your cancel

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Revision date: October 15, 2018

Is the handmade ginger in quality sushi restaurants free?

The ginger served in sushi restaurants is called “gari”. There are people who just chomp down the gari since it’s all free.

However, in certain prestigious restaurants where the gari is handmade, it does end up on the bill. This is because considering the time and ingredients that go into making the gari, the restaurant will be losing money if they don’t charge for it.

However, most sushi restaurants purchase their gari from companies that specialize in it. These mostly include pickling manufactures that have expanded to China or Southeast Asia and have factories there.

When made at these factories, large amounts of ginger is soaked in the stock solution, creating gari in bulk. The quality has improved greatly over the years, but often the fibers are crushed making it soggy, or the gari is stained from ume vinegar.

On the other hand, homemade gari and gari made in Japan is flavored with vinegar and salt while sugar is used sparingly as a subtle flavoring. Handmade gari is crunchy and chewy. The color is also the original pale yellow of ginger.

And during the fresh ginger season at the beginning of summer the price of fresh, domestic ginger jumps up to thousands of yen per kilogram. Since ginger has a high water content, it can be wrung out to reduce 1kg of ginger down to 300g. Making delicious gari by hand costs money. It is also a daunting task of making a year’s worth in advance. Once it’s done there has to be a refrigerator dedicated to storing only the gari.

When you put it that way, homemade gari is far more expensive than its imported equivalent. Providing homemade gari is one of the things that sets sushi restaurants apart from each other. Of course even if you’re not charged for the gari, eating too much will affect your sense of taste for the meal.

What is the difference between “鮨,” “鮓” and “寿司” (all ready “Sushi”).

As far as I know, there are three ways “sushi” is written on sushi restaurant curtains in Japanese kanji characters: 鮨, 鮓 and 寿司.

Do you know the difference? Most Japanese people don’t know the answer to this question.

Broadly, in the Kanto area 鮨 is generally used while 鮓 is more common in Kansai. 寿司 is used commonly everywhere in Japan.

However, of the three, only 鮨 and 鮓 are seen in ancient Chinese literature. 鮨 was seen as a dictionary entry as early as the 5th to 3rd centuries B.C., and it’s origin is described as combining “fish” and “shiokara” (briny flavor) resulting in the term 鮨.

On the other hand, in A.D. 1st to 2nd century dictionaries, “鮓” appeared, and is explained to depict “a storage container for fish.” Toward the end of the second century 鮓 was used for the term “narezushi”.

But around the third century, the briny meaning of 鮨 and the term “narezushi*” written as 鮓 started to be used interchangeably. That is how the words were imported to Japan.

In Japan, the character “鮓” was often used in literature from the end of the Heian era to the end of the Edo era. Eventually the use of “鮨” was revived during the Meiji era (for unknown reasons). It was a natural transition that Kanto came to use “鮨” and Kansai came to use “鮓”.

Incidentally, the kanji “寿司” was created from the phonetics. Its use for celebratory occasions became commonplace throughout Japan.

*”Narezushi” is the primitive version of Japanese sushi. It means covering seafood with salt and then soaking in rice for a few years as a form of lactic acid fermentation, which brings out the acidity.

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Revision date: April 29, 2020

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Assessing Fish at the fish market!

One important task of sushi chefs is going to Tsukiji (Toyosu) every morning, looking at fish with their own eyes and assessing the quality. Having a good eye is important in order to get the highest quality possible, but this is cultivated by experience. They are also constantly obtaining information from the fishmongers at the market regarding what the best fish of the season and their localities. It’s almost a game as to whether they can get high-quality fish at the optimum price everyday. The skills of a sushi chef start with this assessment.

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Revision date: September 11, 2018

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Why do sushi chefs make the sushi in front of the customers?

Many regular patrons of sushi restaurants look forward to having casual conversations with the sushi chefs. It might be difficult to understand for visitors who don’t speak Japanese, but sushi restaurants are the only restaurants in the world that customers can speak directly with the head chef. If you don’t need conversation, then the waiter could just bring the sushi made back in the kitchen. Of course they also want customers to see the beautiful act of making sushi, but there is no particular reason that the sushi has to be made in front of the customer. The technical term for this is “Exposed Business,” meaning that the chefs are putting themselves on display for the customers. Did you learn something new?

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Revision date: September 2, 2018

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About anago, there are two way to make sushi, “skin-up ” and “skin-down”.

Do you know the difference?

The naval (actually the anus) in the middle of the body serves as the border separating the head part (top) and tail part (bottom) of the eel. The fat is distributed better on the top. People used to say that since the bottom moves more it is more tasty, but is this really true?

It’s also often said, “the top should be served skin-up and the bottom should be served skin-down.”

Skin-up means that the skin side is on top and the meaty side is on the rice.

Skin-down means that the meaty side is facing up and the skin side is on the rice.

Conger eel easily melts apart when it is boiled and broth enters the part where it separates, so the appearance is not as appealing. But unless the crack is extremely obvious, both the top and bottom of the conger eel is often prepared skin-down in sushi.

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Revision date: August 27, 2018

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The migrating route of Inshore Pacific bluefin tuna and fishing place!

An illustration of Kuro maguro main prodution area — This is the migration route of Kuro maguro (bluefin tuna).

Tuna caught in the coastal regions of the Japan Sea is notable as the best bluefin tuna in January. Iki, a small island in Kyushu area is one of the famous ports for tuna.

In February and March, the tuna auction market becomes slack due to rough weather. Just a few tunas from Nachikatsuura where is also the famous port for tuna are on the market.

In March and April, tunas become thin because their eggs need many nutrients.

In May, large tuna is seldom seen in the Tsukiji Fish Market. Even if there is, its body is really thin. “Kinkaimono” which means a shore-fish is generally considered as high-class tuna, but in this season, imported tuna is useful instead.

It is said that Pacific Bluefin tunas spawn around Japanese waters between Taiwan and Okinawa in April and May. And then, they go up to fertile, north sea along the eastern coast of Japan.

In June, “Chubo” which is young and small tuna is taken hugely off the coast of the Sea of Japan. The school of Chubo begin moving northward in this season.

In July and August, tunas can be seen occasionally but their bodies are still thin. Instead, Boston Tuna which is caught in the Atlantic Ocean and nicknamed “Jumbo” is on the market. Its fresh is softer than “Kinkaimono” and it doesn’t have medium-fatty part which “Kinkaimono” has.

In September, Boston Tunas are at their best with plenty of fat on them. The best season of Boston Tuna is limited and ends in October. But fortunately, Japanese tunas come into season.

The school of tunas split up into two groups, the one takes Pacific Ocean route and another takes the Japan Sea route and both of them move northward along the Japanese Islands. Some of them reach the Tsugaru Strait where and the season of Tuna begins from September to next January. Oma town and Toi town is famous nationwide for its catch of tuna from the Tsugaru Strait. The flavor of tuna in September is still weak but it becomes stronger in October. In November, feed of tunas such as Pacific saury or Japanese common squid with plenty of fat increase and flavor of tuna also gets stronger. In December, the peak season comes around.

A catch of tuna falls off in January and it enters the final season. The temperature of sea water gets cold and feed of tuna, squids decrease and the fishing season in this area ends.

Tuna is allowed to rest before it is used.

Once a bluefin tuna is caught, it arrives in Tsukiji fish market within a day or two. However, that fish is not used as a sushi topping that day. No mater how good the tuna is, it starts out very stiff and is not in a state where it should be eaten. The meat is hard and the white muscle lines are left in your mouth. The odor and acidic taste of the red meat is strong and the unique sweetness of the fish is nowhere to be found. After it has rested the muscles soften, bringing out the fat.

Then, when the sushi chef gets the tuna, he first separates the red, lean meat and the fatty toro portion, rewraps them separately and, seals them in plastic and puts them on ice. Next is waiting for the “young” meat, not yet suitable for eating, to mature. The number of days the fish will be rested depends on the size of the fish and the temperature. The smaller the cut and the warmer the temperature, the shorter the rest time. Generally the time is from 3-14 days.

This “young” fish not ready for consumption is a fresh, deep color but as it matures the color darkens, the fat is brought out and becomes a fleshy color. Proper care must be taken because if it’s rested for too long, the color changes too quickly.

Why do most sushi restaurants have 8 seats at the counter?

At sushi restaurants, only the master chef makes the sushi. Depending on the shop, the apprentices don’t even touch the knives. The texture of a fish changes greatly with the way a fish is cut, drastically affecting the workmanship of the sushi. There is a clear difference in taste when the master makes a piece of sushi from when the apprentice does. It is also commonly thought that a sushi chef can only take care of about 8 customers at once while he is also preparing pieces of sushi, so most counters have around 8 seats.

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Revision date: August 6, 2018

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Why can’t Sanma (pacific saury) be caught?

On the Pacific Ocean side of Japan there is a three-way deadlock between sardines, mackerel and Pacific saury. There is a theory that the species take turns with increasing and decreasing populations. In recent years there has been an increase in sardines and, in turn, there has been a decline in Pacific saury.

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Revision date: July 30, 2018

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What is the difference between maturing and rotting?

When fish die, stopping the supply of ATP (Adenosine Triphosphate), the source of muscle energy, the muscle fibers gradually harden. As time passes, it gently dissolves and the ATP breaks down, changing into umami components due to self-digestion. The umami created by self-digestion of ATP is “maturing” and the process after that is “rotting.”

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Revision date: July 23, 2018

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